1. Field of the Invention
Embodiments of the present general inventive concept relate to an image forming apparatus to form an image by attaching a recording medium to an image transfer belt (ITB) carrying the recording medium and to easily detach a front end of the recording medium from the image transfer belt (ITB), and a method of controlling such image forming apparatus.
2. Description of the Related Art
Generally, a photo-transfer type image forming apparatus illuminates light on a photo-conductor which is charged with a predetermined potential so as to form an electrostatic latent image. In the image forming apparatus, this electrostatic latent image is developed with a toner used as a developing solution, and the developed image is transferred to the recording medium, such that a color image is formed.
The photo-transfer type image forming apparatus can be classified into an indirect transfer type and a direct transfer type. The indirect transfer type image forming apparatus transfers the image developed on the photo-conductor onto an image transfer belt (ITB), and then the developed image is transferred onto the recording medium. The direct transfer type image forming apparatus directly transfers the image developed on the photo-conductor onto the recording medium transferred by a paper transfer belt (PTB). An image forming apparatus according to an embodiment of the present general inventive concept can be applied to the indirect transfer type and direct transfer type apparatus, such that detachment of a front end of the recording medium may be easily carried out.
For example, the direct transfer type image forming apparatus develops toners of cyan (C), magenta (M), yellow (Y) and black (B) on a photo-conductor on which an electrostatic latent image is formed, and the developed images are sequentially and directly transferred on the recording medium which is moved by a belt carrying the recording medium. The transferred image is fixed by a fixing unit, such that a color image is formed.
In the direct transfer type image forming apparatus, the recording medium is brought into contact with the transfer belt and moves. This recording medium passes respective photo-conductors, such that images overlap with each other on the recording medium, and the recording medium including the overlapped images is transferred. Thereafter, a drive roller makes a detachment angle, such that the recording medium is detached from the image transfer belt (ITB). This recording medium enters the fixing unit, such that the resultant image is fixed onto the recording medium.
In this case, when the recording medium enters the fixing unit after being detached from the image transfer belt (ITB), the recording medium intentionally forms a curl. In this case, if the degree of the formed curl exceeds the intended degree, or if the recording medium is detached from the image transfer belt (ITB) before passing the drive roller after passing the last photo-conductor, a back end of the recording medium may be swept away by a structure positioned between the transfer unit and the fixing unit.
Also, if the recording medium is not detached from the image transfer belt (ITB) at a detachment angle formed by the drive roller when passing the drive roller, or if the recording medium is detached from the image transfer belt (ITB) at another angle behind the detachment angle, the recording medium wrongly enters the fixing unit and collides with peripheral structures of the fixing unit, such that unexpected image distortion arises or the recording medium may be caught in any peripheral structures of the fixing unit without correctly entering the fixing unit. Specifically, if the recording medium is thin and has a high resistance, there are large amounts of charges in the recording medium, and the recording medium is easily bent, such that the recording medium may be wrongly detached from a part where the detachment angle is formed.
The above-mentioned problems may also occur in the direct transfer type apparatus and the indirect transfer type apparatus.